Conventionally, a rotating magnetic field type motor which is provided with a magnet serving as a field source at a rotor side includes a magnet embedded motor which is provided with the magnet embedded in the rotor. JP2000-175388A and JP2004-194472A respectively disclose a fixing structure of the magnet embedded motor. According to the magnet embedded motor disclosed in JP2000-175388A, a fixing spring is provided in a magnet insert hole formed on the rotor and the magnet is fixed by means of a biasing force of the spring. According to the magnet embedded motor disclosed in JP2004-194472A, the magnet is applied with an adhesive (a silicone resin based adhesive, or the like) and the magnet is thereby fixed in the magnet insert hole.
Further, JP2004-48827A (see paragraphs 25-57 and FIGS. 1-5) discloses a rotor of an interior magnet type (i.e., an inner rotor type) brushless motor. More particularly, JP2004-48827A discloses a method for assembling the rotor (i.e., a rotor unit) provided with a cooling fan for cooling the rotor and a magnet sensor for detecting rotation of the rotor used in an electrical tool or an industrial equipment, without difficulty. According to the disclosed interior met brushless motor, the rotor of the motor is rotatably supported by means of a pair of bearings fixed at a frame of the electrical tool. A rotor core having a substantially circular cross section is provided with, at a center part thereof, a rotation shaft insert hole through which a rotation shaft is extended. Further, the rotor core is provided with, at an outer circumferential side thereof, substantially rectangular magnet insert holes into which four tabular main magnets are inserted. The magnet insert holes are arranged into square. Between the rotation shaft insert holes and the mane insert holes, i.e., an inner side of vertex portions of the square, four locking holes are opened. A fan holder formed with the cooling fan is assembled to an end portion of the rotor core, the magnet insert holes of which being inserted with the magnet. The fan holder includes a flat surface which is contacted with the rotor core. Further, the fan holder includes an escape concave portion at a position corresponding to the main agent. Moreover, locking protrusions are provided which are corresponding to the locking hole. By means of the locking protrusions, the fan holder is not rotated relative to the rotor core and the main magnets are not fillen from a fan holder side.
A disk shaped sensor holder is assembled opposed to the fan holder across the rotor core. The sensor holder is provided with locking protrusions corresponding to the four locking holes. By means of the locking protrusions, the sensor holder is not rotated relative to the rotor core and the main magnets are not fallen from a sensor holder side. The magnet sensor provided with a locking mechanism is assembled relative to the sensor holder and fixed by means of thermal welding. If need arises, beings are mounted to both ends of the rotation shaft penetrating through the rotation shaft insert hole after magnetizing the magnet sensor and the main magnet. The rotor assembled in the aforementioned manner is inserted into an inner circumferential portion of a stator which is preliminarily mounted on a frame, and the bearings are fixed to the frame.
However, with the configuration of the above-described conventional magnet embedded motors, an assembling process may occasionally be complicated because of an increase of the number of components and a complexity of the structure thereof. Further, the conventional magnet embedded motor may require a lot of processes for assembling the magnet such as applying the adhesive, inserting the magnet, positioning the magnet, hardening the magnet, or the like. In consequence, the processes for assembling the magnet may harm a retention of a manufacturing cost of the magnet embedded motor and a rotor unit of the motor.
A need thus exists to provide a magnet embedded motor and a rotor unit of the motor, which can readily assembled and effectively reduced in a manufacturing cost thereof.